The invention relates to a device for automatically stacking packages on a support in a predetermined spatial arrangement to form a stack.
Automatic stacking of a support or a carrier, in particular a pallet or a trolley, with packages to form a stack for subsequent shipment, i.e. “palletizing” is known per se. However, in that case packages of uniform size or dimension are placed by robots, grabbers etc. into arithmetically determined locations.
In contrast, the process of automatically loading a load carrier with packages of different characteristics to form a stack is the so-called automatic “mixed-case” palletizing.
Current distribution logistics place ever increasing demands upon picking. Therefore, it is necessary to develop picking systems which process orders automatically without manual intervention.
Thousands of different products (or packages) of the most varied characteristics (size, shape, weight, dimensions, surfaces, solidity etc.) must be picked automatically in such systems.
In that case, it is necessary to take into account various aspects which enormously increase the complexity in comparison with “simple” manual stacking of simple, regular geometries. For instance, a subsequent package can only be stacked or placed effectively onto a preceding package if the latter comprises a flat or planar surface which should also be oriented approximately in a horizontal manner, and if the package can support the weight of the further packages, which are placed thereon, without being damaged.
Furthermore, the stack which is formed should comprise a certain level of stability, inter alia to ensure that it does not fall over during transportation. Although a film wrapping helps, it cannot stabilize an incorrectly formed stack on its own.
Furthermore, customers demand with increasing frequency that the stacks are optimized by reason of the desired unloading sequence.
Therefore, different packages or goods of a different size or dimension are generally still stacked manually, as the requirements placed on the stability of the stack, the packing density within the stack and the sequence of loading and the resulting unloading sequence and not least the stacking capability of the goods are extremely high and to date have not been fulfilled or have only been partly fulfilled by the known methods and devices.
EP 1 462 394 B1 discloses a device for automatically loading a load carrier with packing units which form a stack, i.e. a device for palletizing. In the case of the device, the packing units are fed lying supported and individually on trays from where they are placed onto a packing table. At this location, the packing unit, lying on the table, is displaced by a pusher along the broad side of the pallet to be loaded until the loading coordinates in the X-direction are reached. Subsequently, a further pusher and a loading tongue simultaneously push the packing unit in the direction of the load depth over the pallet until the loading coordinates in the Z-direction are reached. Subsequently, the loading tongue moves back, wherein the pusher remains stationary and serves as a scraper, so that the packing unit is placed “free-falling” at the desired position on the pallet. The stack which forms is supported by a loading aid on the remaining three sides. Stacking thus occurs as it were “against the wall”. However, the displacement on the packing table is time consuming and owing to the restricted accessibility has disadvantages when forming the packing patterns. Moreover, it is vital that the loading tongue and the scraper/pusher move simultaneously in the X-direction. Also, only one packing unit can ever be “processed” sequentially.
WO 2010/059923 A1 discloses an automatic robot-assisted device for stacking, in which an intermediate plate is used for forming the first tier of a stack and simultaneously changing the pallet.
There is a greater requirement for the stacked packages to be provided in so-called trolleys or rolling containers. They can be loaded easily into trucks and unloaded in situ and moved, as they comprise rollers. Moreover, they comprise sidewalls which permit stable stacking and effective stabilization by means of stretch film, so that transportation is likewise secure. However, these characteristics cause problems during automatic stacking.